The invention relates to a countersteering rear vehicle axle which, under the effect of a lateral force upon the wheel that is outside during cornering and is fastened to a wheel carrier, causes a rotational movement of this wheel carrier about a virtual steering axle inclination in the toe-in direction. The wheel carrier is supported by way of supporting elements on an axle body extending essentially in the longitudinal direction of the vehicle. Concerning the known state of the art, reference is made, for example, to German Patent Documents DD 281 154 A5 as well as DE 103 21 877 B4.
It is known that basic rear vehicle axles, particularly of the compound link type, but also of the longitudinal link and trailing arm type, may have an oversteering tendency under the influence of lateral force. Remedial measures against this tendency are also already known from the above-mentioned state of the art. Thus, German Patent Document DE 103 21 877 B4 shows a wheel carrier bearing with a so-called swing plate, in which four elastic pivot bearings are integrated. By way of this extremely high-expenditure construction, under the influence of lateral force, the wheel on the outside during cornering is steered in the toe-in direction and the wheel on the inside during the cornering is steered in the toe-out direction, whereby the axle has a stabilizing effect. The same takes place in the case of a constructively considerably simpler, so-called countersteering rear axle according to the German Patent Document DD 281 154 A5, but the structural durability of a plate-shaped spring element that is provided there and carries the wheel carrier leaves a great deal to be desired.
There is therefore needed a relatively simply constructed so-called countersteering rear axle which meets the general durability requirements of vehicle axles for example for passenger cars.
This need is met in that two torsionally soft but bending-resistant supporting elements are, in each case, provided above and below the wheel center. In a lateral projection comparable to the virtual steering axle inclination, the supporting elements are essentially equally inclined with respect to the vertical direction. An upper linkage supporting element, which extends essentially in the transverse direction of the vehicle toward the inside, is supported, on the one side, on the wheel carrier and, on the other side, on an upper torsion supporting element which, by means of its other end, is supported on the axle body, while a lower linkage supporting element, which extends essentially in the vertical direction, is supported on the wheel carrier, on the one side, and on a lower torsion supporting element, on the other side. The lower torsion supporting element is supported on the axle body by means of its other end.
The wheel carrier is supported on the axle body by at least four supporting elements, which axle body may, for example, be the longitudinal tube of a compound link or a link in general (longitudinal link or trailing arm) of the wheel suspension. Each of these supporting elements has an essentially bend-resistant but torsionally soft construction. Because of the bending resistance of these supporting elements arranged as indicated above, a sufficiently structurally durable support is provided with respect to longitudinal forces as well as vertical forces acting upon the wheel or upon the wheel carrier. However, as a result of the torsional softness of these elements, a desired slight torsion of the wheel or the wheel carrier under the influence of lateral force becomes possible about a steering axle inclination (also called steering axle) formed essentially by these supporting elements or their “thrust centers,” which will be further discussed in the following. In this case, an arrangement of four such supporting elements, which are each formed by appropriately shaped longitudinal profiles, is considerably simpler constructionally than, for example, the arrangement with four elastic pivot bearings known from the above-mentioned German Patent Document DE 103 21 877 B4.
As far as the design and arrangement of the, in each case, essentially bend-resistant but torsionally soft supporting elements in the form of longitudinal profiles, i.e. of profiled rods, each having a suitably profiled cross-section, are concerned, the supporting elements arranged above the wheel center and the supporting elements arranged below the wheel center preferably are to be designed and arranged such that, viewed in the transverse direction of the vehicle, the thrust centers of the upper supporting elements are situated significantly closer to the center of the vehicle or of the axle than the thrust centers of the lower supporting elements. In other words, this means that, viewed in the transverse direction of the vehicle, the thrust center of each supporting element situated above the wheel center is situated at a significant distance from the thrust center of each supporting element situated below the wheel center. As known, the thrust center (also called lateral-force center or torsional point of rest) of a profiled cross-section is that point through which the resultant force of the transverse forces acting upon the profiled cross-section has to extend when a no-torsion force effect is to be reached and therefore no torsion is to be exercised upon this profiled cross-section.
A preferred profiled cross-section, by which a corresponding position of the thrust centers, by which finally the position of the virtual steering axle inclination of the wheel carrier is also defined in space, can easily be implemented, is formed by an essentially U-shaped profile whose thrust center, as known, is situated outside the profiled cross-section below the base of the profile. When profiled rods are used as the supporting elements which are essentially U-shaped in their cross-section, it is therefore recommended to arrange the two supporting elements that are above the wheel center (but at least the upper so-called torsion supporting element) such that the two legs extend in the transverse direction of the vehicle and the profile base faces the center of the vehicle; i.e. that the profile is open toward the wheel. In contrast, the two supporting elements that are below the wheel center (but at least the lower so-called torsion supporting element) should be arranged such that the two legs extend in the transverse direction of the vehicle and the profile base faces the exterior side of the vehicle; i.e. the profile is open toward the vehicle center.
In this case, it should be pointed out explicitly that the use of U-profiles is definitely not required for achieving the effect according to the invention, although the best result may be achieved in this manner. For the supporting elements, profiles having a semicircular cross-section or profiled rods or longitudinal profiles having a T- or L- or X-cross-section, or other suitable cross-sections, can be used as an alternative. (Reference will be made to the preceding statements concerning the thrust centers of the individual supporting elements at a later point in the description of an embodiment in the figures under the term “thrust center theory”).
Viewed in the longitudinal direction of the vehicle, the virtual steering axle inclination is defined essentially by the two torsion supporting elements and—depending on the profiled cross-section selected for these torsion supporting elements or for all supporting elements—can essentially extend in the direction of the upper and of the lower torsion supporting element. Preferably, these (as well as the virtual steering axle inclination) are inclined in the transverse direction of the vehicle essentially in the same manner with respect to the vertical line such that a negative steering offset is formed—for achieving its basically known advantages. In particular, by way of such a negative steering offset during braking operations and therefore under the influence of longitudinal force, a desired moving of the wheel in the toe-in direction can also be generated, i.e., the wheel or the wheel carrier can be swung about the virtual steering axle inclination in the toe-in direction.
In addition to being supported by the above-mentioned four supporting elements, the wheel carrier can be supported, preferably again on the above-mentioned axle body, by at least one additional connecting element away from the steering axle inclination, which connecting element has a certain softness. This softness permits the desired swinging motion of the wheel carrier about the virtual steering axle inclination, in which case this connecting element can influence and particularly also dampen the intensity of the swinging motion. For example, a rubber bearing, which is soft in the axial direction, can be used as such a connecting element, the axial direction extending tangentially with respect to the rotating direction of the wheel carrier about the virtual steering axle inclination. As a result, the torsional softness about the steering axle inclination can be adjusted and thus also the elasto-kinematic toe-in steering behavior of the axle. As mentioned above, such a connecting element having a certain softness can dampen particularly torsional vibrations about the virtual steering axle inclination and furthermore reduce the axle windup during braking operations. In addition, such a connecting element can transmit forces during the compression of the wheel. Advantageously, toe adjustment of the axle can also be carried out at this point. It is also explicitly pointed out again that a rubber bearing does not necessarily have to be used as the connecting element, but rather the connecting element can also be formed by a suitable structural component that has the above-mentioned “softness” in the above-described direction.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.